Configure release workflow

[crandmck]

Create release workflow to keep GitHub releases https://github.com/contentauth/c2pa-python/releases in sync with PyPI releases.

Per @raymurillo, it’s only pushing to PyPI here: https://github.com/contentauth/c2pa-python/blob/main/.github/workflows/build.yml#L360-L379.

[tmathern]

Note this changed a little bit in the meantime. Pushing to PyPI now happen here: https://github.com/contentauth/c2pa-python/blob/main/.github/workflows/build.yml#L464-L472. There is still no auto-tagging or no auto-increment of version numbers though.

[tmathern]

I realize that I think we can close this to the benefit of #58.